As to a conventional intake pipe of an internal combustion engine, Japanese Patent Laying-Open No. 7-19132, for example, discloses an intake device for a V-type engine intended for changing the direction of an opening by reducing a protrusion amount of an upper stream side intake channel above the engine and by avoiding interference with a cylinder head cover. In this document, the intake device is mounted on a transversely-installed V-type six-cylinder engine where a front bank and a rear bank are installed in a V-shape, each of the front bank and the rear bank being formed of a cylinder group including cylinders whose intake strokes do not occur successively. The intake device has a surge tank having a two-tiered structure. At the surge tank, an upper surge tank communicating with the rear bank and a lower surge tank communicating with the front bank are integrally formed.
In the V-type six-cylinder engine disclosed in the above-described document, an intake stroke alternately occurs at the front bank and the rear bank, and hence an airflow that flows back and forth between the upper surge tank and the lower surge tank in the surge tank is generated. However, if the air does not flow smoothly when it moves around an end portion of a partition wall that allows the upper and lower surge tanks to be apart, improvement in intake efficiency of the engine may be hindered.